The tank vent comes back up to the input tube just below the cap about 2 or 3 inches. With a flashlight push open the metal cover and look for any blockage. You can better understand what I'm talking about here. These are the components of your system.

The tank vent comes back up to the input tube just below the cap about 2 or 3 inches. With a flashlight push open the metal cover and look for any blockage. You can better understand what I'm talking about here. These are the components of your system.